


Fraternal Instinct

by Aryū Muin (Caeslin)



Category: Hunter X Hunter
Genre: Extremely Dubious Consent, M/M, Mating Cycles/In Heat, Restraints, Sibling Incest
Language: English
Status: Completed
Published: 2020-05-02
Updated: 2020-05-02
Packaged: 2021-03-02 05:35:05
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings, Underage
Chapters: 1
Words: 754
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/23960044
Author URL: https://archiveofourown.org/users/Caeslin/pseuds/Ary%C5%AB%20Muin
Summary: It's Killua's first heat, and Illumi is here to see him through it safely.
Relationships: Illumi Zoldyck/Killua Zoldyck
Comments: 8
Kudos: 236





	Fraternal Instinct

**Author's Note:**

> Written for the prompt "helping a family member through their heat"; because as we know from canon, Illumi is great at helping.

There's no question of letting Killua out of the compound like this, of course. He can't be trusted to make intelligent decisions in his current state, and while his personal safety is no issue -- he hasn't been trained for nothing -- it would be inconvenient if he were to relieve his urges with someone unsuitable or, god forbid, get it in his head to strike up a pair bond. When he's older and more level-headed, his control over his instincts more finely honed, he will of course be allowed the freedom to do as he pleases. But for now, while he's still a child, he's safest under the watchful eye of his family.

First heats are particularly volatile. Killua is weathering this one well so far, but one never knows when it might turn. Mother and Father checked in often during the first day, but they can hardly afford to abandon their duties, so it falls to Illumi, as the eldest, to supervise him in their stead. It's a responsibility he takes very seriously.

Though he must concede it's also a pleasure to have his little brother all to himself. Killua's breath is heavy as Illumi strokes his cheek, his skin hot to the touch. He's radiating so much scent it's a wonder the whole corridor doesn't reek of him. This close, Illumi feels his own blood stirring despite the fact that he's weeks out from his own season. Perhaps it's that awakened instinct that compels him to caress the back of Killua's neck.

It hasn't been an hour since Illumi wrung his last orgasm out of him, but still Killua arches into the physical contact as though he's never been touched before. He's beautiful like this, straining against his shackles. 

"Please," he says, voice ragged. "Illumi. I can't ..."

Killua would never beg him under normal circumstances. Illumi ought not to let him get away with such displays of weakness now, no matter the novelty value; yet a perverse part of him wants to tease Killua regardless. He gave into the temptation yesterday, stringing him out until he was sobbing with arousal, begging through tears for Illumi to give him the touch he craved. Killua's desperation sounds far sweeter than it should, and Illumi still hasn't quite reconciled his own attachment to it.

Today Illumi is feeling more indulgent, and so he takes Killua's straining length readily in hand. The touch elicits a broken moan.

"Are you so hungry for this?" he murmurs, relishing how the words make Killua's whole body tremble. "You mustn't feel ashamed, you know. It's in your nature."

In truth, any shame Killua may once have felt almost certainly burnt off days ago. On the first evening, he'd resisted Father's hands as he forced him into the chains, bristling at any offer of touch; but one night alone reduced him to a feverish, shivering wreck, barely able to lift his head at Illumi's approach the following morning. When Illumi turned his chin up, then pressed those same fingers against his lips, he'd accepted them onto his tongue without the slightest hesitation.

Now, he whimpers as Illumi slides his fingers back to trace his swollen entrance. Killua is dripping for him, his muscles twitching with the need to be filled.

"Be patient, Killu. I know what you need."

Illumi can't claim Killua the way his body yearns for -- never mind that he's not in rut himself, it wouldn't be proper -- but his fingers make an agile, practiced substitute. He works Killua open with one hand while milking his cock with the other, until Killua is gasping breathlessly into the curve of his neck. Illumi almost regrets that their profession doesn't allow Killua to show this side of himself more often. He thinks Illumi doesn't know why he chafes against the family's discipline, but privately Illumi understands his resentment all too well; if he could somehow split Killua in two, it's this yearning, trembling, breathtakingly raw half that he would keep.

"Illumi -- Illumi --"

Mindful of the volume of his voice, Illumi silences him with a kiss. Killua's mouth opens hot and sweet beneath his own, his muffled cries as smooth as honey on Illumi's tongue.

Illumi really is growing dangerously sentimental. Perhaps his season is more imminent than he assumed, though it's just as likely that Killua himself is to blame. For all that he needs to learn obedience, and self-discipline, and all those other traits best cultivated through a firm hand, Illumi can never seem to resist the urge to spoil him.


End file.
